Abstract
We discuss the physics of kink waves of dislocations of density nd and their Bose-Einstein condensation (BEC). The BEC of the kinks makes possible dissipationless movement of the dislocation lines (quantum plastic flow). We estimate the superfluid fraction f of 4He atoms and find that because of the long range strains caused by the dislocation the corresponding superfluid fraction f due to the motion of the dislocation lines is larger than the simplistic estimate of nda02 by a factor L/a0 where a0 is the lattice constant, L is the average mosaic size. With experimental estimates of nd ranging from 6x109/cm2 to 106/cm2, we get f ranging from 72% to 0.07%, consistent with experimental results. Because the spatial derivative of the strain field of a disloaction is odd under a spatial inversion, the net sum for the displacement caused by the dislocation motion is zero. The dislocation motion only affects the rortational motion and does not produce any net linear motion of the atoms and thus will not generate any direct superflow, also consistent with experimental observations.
Coffee and tea will be served 20 minutes prior to the seminar.